Rheostat.



UNITED STATES PATENT ()EEICE VILLIAM II. CIIAPMAN, 0F PORTLAND, MAINE.

RHEOSTAT.

SPECIFICATION :forming part of Letters Patent No. 705,561, dated July29, 1902.

Application led December 14, 1901. Serial No. 85.872. (No model.)

To all whom t mag/concave:

Be it known that I, WILLIAM H. CHAPMAN, a citizen of the United Statesof America, and a resident of Portland, Cumberland county, State ofMaine, have invented certain new and useful Improvements in Rheostats,of which the following is a specification.

My invention relates to rheostats, and particularly to an improvedconstruction of the segments by which I am enabled to operate therheostat with very little friction; and it is designed to be used inautomatic machines like voltage-regulators, where it is important tohave little friction and extreme sensitiveness. Thesedevicesareprovidedwithswinging arms operated by solenoids or othersimilar means, and these arms are provided with spring-pressed contactswhich slide along the segments as the arm swings back and forth to throwin more or less resistance. It is obvious that the wider the segmentsover which the contact has to travel the greater must be the distance itmust travel to throw in a given number of resistances and the morefriction must be developed in the operation of the device.

The object of my invention then is to narrow up as much as possible thewidth or thickness of the segments over which the contact slides, and todo this I make use of comparatively thin segment-plates, clamping themtightly together at the front with the proper insulating materialinterposed between themV and extending and spreading the rear ends togive room for making the proper connections With the wires. Half of therear portion of each segment is cut away, the upper half on every otherone and the lower half on the remainder, so that the rear ends of eachtwo adjacent segment-plates may be swung by each other to allow room forsoldering, the. In this way it is possible to crowd in a great number ofsegments in a small space, at the same time leaving their rear endssuffi ciently apart for soldering the wires.

I illustrate my invention by means of the accompanying drawings, inwhich-- Figure 1 isa front view of a portion of the voltage-regulatorpatented to me May l, 1900, with my improved segments in place. Fig. 2is a plan view of the segments on an enlarged scale, and Fig. 3 is asection taken on the line oc a? of Fig. 2.

A represents the frame.

B B are the solenoids; b I), the cores of the solenoids; c c, theconnecting-rods, and D the T-shaped lever, having two horizontal armsconnecting with the cores b and a vertical arm d, carrying aspring-pressed contact, here shown as a lever, having a vertical arm e,connected by a spring to the arm d, and a contact-finger c', adapted toslide over the upper edges of the contact-plates.

The above-described parts or their equivalents are common to my patenteddevice and need no further description.

For the purpose of decreasing the friction between the contact-point andthe segmentplates and to bring as many segment-plates as possible withinthe limits of movement of the contact I form the segment-plates g ofcomparatively thin sheets of coppeigwith thin sheets 7i of insulatingmaterial between themh The front ends of these plates are firmly clampedtogether in the frame il by means of set-screws j, acting against apressure-bar l, sheets of mica 7c being interposed between the endsegmentsf and the adjacent parts of the frame and beneath the segments.The upper surface of the segment-section is made concave to conform tothe pathof the contact-finger e, and the rear ends of the segment-platesare extended rearward a considerable distance and are provided withloops g2 to receive the wires necessary to connect them with theresistance units. These segment-plates are made just thick enough tocarry the necessary current and no thicker, so that as many as possiblemay be put within the limits of motion of the contacts e', In order tospread the rear ends so that 'the loops g2 will not interfere with eachother, I

.cut away the rear ends of the plates, a trifle more than, half beingcut from each one, first the upper half of one plate and the lower halfof the next plate. rlhis enables two adjacent loops to swing around soas to clear each other, and the result is that the loops take uponlyone-half the space horizontally 4that they otherwise would. v Itwill be seen that with this arrangement of segments the sensitiveness ofmy regulator is greatly increased IOO as the friction is reduced, sincethe distance which the cont-act has to travel is reduced, and a smallmotion of the cores of the solenoids and of the arm CZ Will throw in ortake off a comparatively large number of resistance units. By the use ofa large number ot' segments and resistance units the changes of voltageare effected more gradually than where a small number are used.

I have illustrated my device as applied to my voltage-regulator; hut itis evident that it may be used on devices similar in character Working,`automatically.

I claim- In a rheostat7 the combination ol' a swinging arm, aspring-pressed contact 0n said arm,

a series of thin segment-plates on which said contact is adapted totravel, insulating-plates between said segment-plates, saidsegmentplates being closely clamped together at their front ends an dspread apart at their rear ends, the upper half ol the rear portion ofevery other plate and the lower half of the balance of the platesbeing,` cut away so that the rear ends of adjacent plates may be ewungover each other.

Signed at Portland,'Maine, this 0th day of December, 1901.

WILLIAM ll. CHAPBLIAN. \Vitnesses:

W. BATES, L. M. GODFREY.

